The advent of digital cinema has created new standards for cinema sound, such as the incorporation of multiple channels of audio to allow for greater creativity for content creators and a more enveloping and realistic auditory experience for audiences. Model-based audio descriptions have been developed to extend beyond traditional speaker feeds and channel-based audio as a means for distributing spatial audio content and rendering in different playback configurations. The playback of sound in true three-dimensional (3D) or virtual 3D environments has become an area of increased research and development. The spatial presentation of sound utilizes audio objects, which are audio signals with associated parametric source descriptions of apparent source position (e.g., 3D coordinates), apparent source width, and other parameters. Object-based audio may be used for many multimedia applications, such as digital movies, video games, simulators, and is of particular importance in a home environment where the number of speakers and their placement is generally limited or constrained by the confines of a relatively small listening environment.
Various technologies have been developed to more accurately capture and reproduce the creator's artistic intent for a sound track in both full cinema environments and smaller scale home environments. A next generation spatial audio (also referred to as “adaptive audio”) format has been developed that comprises a mix of audio objects and traditional channel-based speaker feeds along with positional metadata for the audio objects. In a spatial audio decoder, the channels are sent directly to their associated speakers or down-mixed to an existing speaker set, and audio objects are rendered by the decoder in a flexible manner. The parametric source description associated with each object, such as a positional trajectory in 3D space, is taken as an input along with the number and position of speakers connected to the decoder. The renderer utilizes certain algorithms to distribute the audio associated with each object across the attached set of speakers. The authored spatial intent of each object is thus optimally presented over the specific speaker configuration that is present in the listening environment.
Current spatial audio systems have generally been developed for cinema use, and thus involve deployment in large rooms and the use of relatively expensive equipment, including arrays of multiple speakers distributed around a theater. An increasing amount of advanced audio content, however, is being made available for playback in the home environment through streaming technology and advanced media technology, such as Blu-ray disks, and so on. In addition, emerging technologies such as 3D television and advanced computer games and simulators are encouraging the use of relatively sophisticated equipment, such as large-screen monitors, surround-sound receivers and speaker arrays in home and other listening environments. In spite of the availability of such content, equipment cost, installation complexity, and room size remain realistic constraints that prevent the full exploitation of spatial audio in most home environments.
Object-based (e.g., adaptive) audio in the home environment consists of audio signals being presented to the listener originating from in front of and around the listening position in the horizontal plane (main speakers) and overhead plane (height speakers). A common object based audio playback system will consist of front, side and back surround, height loudspeakers and subwoofer. A full home enabled loudspeaker system layout will typically consist of: front loudspeakers (e.g., Left, Center, Right, and optionally Left Center Right Center, Left Screen, Right Screen, Left Width, and Right Width), Surround loudspeakers (e.g., Left Surround, Right Surround, and optionally Left Surround 1, Right Surround 1, Left Surround 2, Right Surround 2), surround back loudspeakers (e.g., Left Rear Surround, Right Rear Surround, Center Surround, and optionally Left Rear Surround 1, Right Rear Surround 1, Left Rear Surround 2, Right Rear Surround 2, Left Center Surround, Right Center Surround), height loudspeakers (e.g., Left Front Height, Right Front Height, Left Top Front, Right Top Front, Left Top Middle, Right Top Middle, Left Top Rear, Right Top Rear, Left Rear Height, Right Rear Height), and subwoofer speakers. Loudspeakers come in various types, such as: in-room (traditional box speakers on a stand or in a cabinet); in-wall (traditionally mounted in the wall in the horizontal plane around the listener); on-wall (traditionally mounted on the wall in the horizontal plane around the listener) d) in-ceiling (traditionally in the ceiling above the listener for the surrounds and far forward for the fronts); and on-ceiling (traditionally on the ceiling above the listener for the surrounds and far forward for the fronts). Depending upon personal taste and the physical and aesthetic restrictions that are placed upon them by the homeowner, the user's loudspeaker system can be exclusive to each of the above loudspeaker types or any combination of the above loudspeaker types.
Ceiling (in-ceiling or on-ceiling) or upper wall mounted speakers (collectively referred to as “downward-firing speakers”) are becoming increasingly used in home playback systems. Such speakers represent a good solution for homeowners that are unable or unwilling to use in-wall, on-wall or in-room loudspeakers. This could be because homeowners have windows, doors, walkways or artwork in the way for in-wall loudspeakers or simply no space for in-room box type loudspeakers. In these commonly occurring situations ceiling loudspeakers often represent the only alternative, leading to their popularity.
To recreate the intended adaptive audio experience in the home, audio is necessary to arrive to the listening position from common main outputs (left, center, right, left surround, right surround, left back surround and right back surround) as well as from height outputs. Currently, ceiling type loudspeakers are only designed to play back audio associated with height outputs from single sources. This ceiling loudspeaker needs to provide not only the audio from the height outputs but also audio for the main outputs where necessary in the home installation, i.e. front, side surround and back surround. In many cases, and especially in the home environment, direct speakers may not be available. In this case, the direct information is lost if such sound objects are played only through ceiling mounted speakers.
What is needed, therefore, is a system that allows full spatial information of an adaptive audio system to be reproduced in a listening environment that may include only a portion of the full speaker array intended for playback, such as ceiling speakers only with no direct speakers.
The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also be inventions.